Chevrolet 2005 Astro Owner's Manual page 251

Checking Brake Fluid
You can check the brake fluid without taking off the cap.
Just look at the brake fluid reservoir. The fluid level
should be above MIN. If it is not, have your brake
system checked to see if there is a leak.
After work is done on the brake hydraulic system,
make sure the level is above the MIN but not over the
MAX mark.
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